Quenched-spark gap, especially for overvoltage suppressors



Jan. 26, 1960 R. GREUTER 2,922,915 QUENCI-IED-SPARK GAP, ESPECIALLY;

FOR OVERVOLTAGE SUPPRESSORS Filed March 5, 1958 Fig. 7

United States Patent QUENCHED-SPARK GAP, ESPECIALLY FOR OVERVOLTAGE SUPPRESSORS Robert Greuter, Zurich, Switzerland, assignor to Oerlikon Engineering Company, Zurich, Switzerland, a corporation of Switzerland Application March 5, 1958, Serial No. 719,320

2 Claims. (Cl. 313-325) This invention relates to a quenched-spark unit, especially for overvoltage suppressors, consisting of quenching plates or electrodes formed at their circumference or in its vicinity with trough-like recesses, said electrodes being separated from each other by annular insulating spacers.

The overvoltage suppressors hitherto used contain mostly two basic elements viz. the quenching gap and the valve-like acting resistances which are dependent on the voltage. The quenched-spark gap is usually built up by a number of specially shaped plates i.e. the quenching plates. Fig. 1 of the attached drawing shows a well known arrangement of plates, wherein the active planes of two adjacent quenching plates are marked 1 and 2.

The central bores 1 and 2 are conditioned by the man-- ufacturing process. Near their circumferences said plates have the recesses 3 and 4. The distances between the plates is determined by means of the insulating ring 5. Said distance forms the partial spark gap. The number of required partial spark gaps increases when the operating voltage rises. The insulating ring 5 should be of such size and the form of plates should be chosen in such a manner that a flashing-over occurs only upon the active planes of plates provided for this purpose, but not in proximity to the insulating discs. Should the flashover take place at the insulating discs, a conductive path will be formed there and the subsequent ignitions will be repeated at the same place. Due to this circumstance the working voltage is varied and drops rapidly in such a manner that it does not exceed essentially the normal service voltage. This will lead to frequent ignitions and thus to an overcharging of the resistances dependent on the voltage. Thus the service life of the overvoltage suppressors will be considerably reduced. In the arrangement of plates as per Fig. 1 the described disadvantages occur. To avoid the deficiencies of the known quenched spark gaps, it has been proposed to fix the quenching plates on a rod of ceramic insulating material in absence of insulating intermediate layers. The disadvantage consists in the fact that the width of air-gaps cannot be maintained with full accuracy. Finally it is to be added that an essential magnification of recesses 3 and 4 and reduced active areas 1 and 2 does not create any remarkable improvement. The are is indeed always blown outwards by a thermic elfect (arc distances 6 and 7 of Fig. l) and finally adheres to the insulating rings.

This difiiculty will be overcome by the arrangement as per the invention according to which the active plate planes of adjacent quenching plates forming a partial spark gap have unequal diameters.

Fig. 2, representing the same parts with the same reference numbers as in Fig. 1, shows a pair of plates according to the invention. Thorough tests have shown that the are 8 cannot go outwards at will. It runs first into the recess of the electrode with the smaller active plane (are 9) and quenches before leaving the larger active area. In such a way a deterioration of the insulating rings is with full certainty avoided.

The drawing shows each time only one pair of plates.

Those pairs can be combined in a pile equipped with end plates and cast around with resin.

What I claim is:

1. A quenched-spark gap unit comprising a pair of disk-like electrodes separated at their margins by an annular spacer of insulation, each electrode being shaped to define a central active area surrounded by an annular trough adjacent to the margin of the electrode, said active areas being in parallel spaced concentric relation, the active area of one electrode being larger than the active area of the other, the trough of the electrode with the larger active area being narrower than the trough of the other electrode, said troughs being in opposed relation to form therebetween an annular chamber of constant cross-sectional configuration throughout its extent.

2. A quenched-spark gap unit comprising a pair of disk-like electrodes separated at their margins by an annular spacer of insulation, each electrode being shaped to define a central active area surrounded by an annular trough adjacent to the margin of the electrode, said active areas being in parallel spaced concentric relation, the active area of one electrode being larger than the active area of the other, the trough of the electrode with the larger active area being narrower than the trough of the other electrode, said troughs being in opposed relation to form therebetween an annular chamber of constant cross-sectional configuration throughout its extent, and said spacer extending partially into said chamber.

References Cited in the file of this patent UNITED STATES PATENTS 330,486 Holt Nov. 17, 1885 2,571,814 Beck Oct. 16, 1951 2,623,197 Kalb Dec. 23, 1952 

